Peer-reviewed by 2 reviewers with median rating of 17/20. Review process was triple-blinded.

Round 1 (17/20)

Technical quality9

Conceptual advance and Impact9.5

General comment

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The manuscrip looks good in its content and wrting. It contains new findings and valuable information for marine ecologists. My only concern is that why the author do not identify the species directly as Nanipora kamurai, instead of using Nanipora cf. kamurai. This should be an easy task for the author.

Technical quality7

Conceptual advance and Impact8

General comment

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Climate change and anthropogenic activities threaten the survival of organisms associated with coral reefs and seagrass beds, and hence this manuscript is timely as it emphasizes the presence of an understudied group of Octocorallia in those ecosystems. The manuscript focusses on rare benthic organisms found in a remote atoll in the South China Sea, for which most of the diversity and ecology have to be explored. The manuscript is well-written and the results are interesting. Overall, this study represents a valuable contribution to scientific knowledge and I highly recommend its publication.

Abstract

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I would recommend to provide the latitude and longitude of Dongsha

Figure

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I would reccomend to provide an approximate scale bar on the images of Nanipora and also a map of Dongsha Atoll with a vague approximation of the area surveyed around Dongsha Island. I could not find the Supplemental Fig. 1.

Introduction

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In the first sentence, please change "fossil" to "fossils".
I would suggest to combine these two sentences, which are a bit redundant: "The most recent group described was the monotypic genus Nanipora from shallow coral reefs in Okinawa ([3]). Surprisingly, unlike other Lithotelestidae reported until now, N. kamurai was found to inhabit shallow coral reefs." For example: "The most recent group described was the monotypic genus Nanipora Kamurai from Okinawa ([3]) and unlike other Lithotelestidae reported until now, N. kamurai was found to inhabit shallow coral reefs."

Results & Discussion

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Although I understand why the authors did not want to provide the exact locations of theirs surveys, I think they could specify in which other areas of the atoll they also explored without providing their exact locations. Did they include other areas around Dongsha Island, arears in patchy reefs in the lagoon in proximity with other seagrass bed areas or even on the reef flat?
I am a bit surprised of the way the authors have expressed the depth. It is more typical to say something like "X meters relative to the mean sea level".
Please specify that Syringodium isoetifolium is a seagrass species.
I think the authors of the citations should be provided before each number in the following sentence: "Additionally, while[3] reported only encrusting N. kamurai from Okinawa,[5] reported on occasional laminar growth of N. cf. kamurai."
In order to avoir repetition, replace "known" by "recorded up-to-date" or by another synonym in the following sentence: "The population of Nanipora at Dongsha Atoll represents by far the largest known population of this relatively unknown genus."
Replace "studied" by "investigated" in the following sentence: "The ecology of Nanipora remains to be studied, and future studies should therefore examine not only coral reefs, but also seagrass beds."
For accuracy, I would recommend to add a sentence with the appropriate citation, which states that Dongsha Atoll is a Marine Protected Area, albeit some illegal fishing are still occurring (as the authors wrote down).
The authors may also want to emphasize that Dongsha Atoll has alreedy lost many seagrass bed areas (especially on the reef flat) and potentially some undiscovered colonies of Nanipora could have also been lost. Like the authors mentioned, understanding the ecology of Nanipora is therefore a very critical topic that should be tackled very quickly.